MXDL CR123 rebuild: fully regulated or buck?

I'm about to rebuild this with a SSC P4 and multimode driver, but I can't decide whether to go for this fully regulated driver (which I hope I can mod down to 6-700mA or such; it outputs 1A stock, which is too much for the unimpressive heat management of the MXDL) or this AMC buck one (unsoldering one of the AMC chips will get the current down to 700mA).
Modes aren't a problem, as I plan on modding them to get my personalized interface.

I like full regulation and I use it whenever I can on my 18650-powered lights, but 18650 cells have tons of capacity and don't have much trouble delivering more current as their voltage sags to keep the driver happy. I'm not sure if RCR123s would be as happy with that treatment. Perhaps it'd be better to be gentler on them as they lose charge?
On the other hand, the buck-only driver would be pretty much useless on primary cells. Ok, I practically never use them, but it's nice to have the option if need be.

Opinions welcome.

Bump!

Hey... nice to see someone else getting into mods. I have come to the realization that no one really makes an 18650 light that meets my requirements so i am having to resort to DIY mods.

I think you should also consider DX7882. I am very happy with this one, and have modded a couple P60 modules and a Lowes task force with it. FIY, you can adjust the MAX current output on 7882 with the small pot. So you might not need to remove ICs or reprogram the UI algorithm. I have one module set up to send 1300mah to the emitter on HIGH. Medium is 50% and low is 10%. So I get a long running low mode at around 180mah / 15L with a Cree-R2, medium is right around 650mah (perfect for your application). In case you ever need it high is still accessible for limited spot-use. Most of the time I keep it on Low-Medium and its perfect. FWIW, P60 modules dont have great thermal management either, so I have to use discretion. Nice thing about this board is that it does not exhibit PWM flickering at all, and contrary to the DX description there is a plain L/M/H mode group... no strobes.

the second module I have updated uses a Cree-P4, I have it adjusted to emit the lowest possible amount of light to extend run times, 8-9 Lumens in low and about 120L in high. Its one of my favorite lights.

You should also note that the DX7882 board has a design flaw. You need to bridge V+out over to C1. If you don't the circuit does not work.

Someone... I think SteffanFS did some detailed current measurements and efficiency calculations. Its either on CPF or the DX forums, I can't remember.

Thanks, but I'm not waiting another month for another DX order. I've decided to go for the buck driver minus one AMC, since I have no easy way of getting the regulated one down to the output I want. I might be able to do it by replacing resistors and all, but frankly it's not worth the trouble.